The compounds of the instant invention are polar compounds designed to have a low log D and thereby have a limited ability to cross the blood-brain barrier. This means that the side effects associated with centrally acting kappa opioid agonists are greatly reduced upon administration of these compounds to a mammal, preferably a human, in need of treatment. Such side effects are various CNS problems and dysphoria.
The compounds of the instant invention are compared to [5R-(5.alpha.,7.alpha.,8.beta.)]-N-methyl-N-[7-(1-pyrrolidinyl)-1-oxaspiro -[4,5]dec-8-yl]-4-benzofuranacetamide, monohydrochloride, which is described and claimed in U.S. Pat. No. 4,737,493 which patent is hereby incorporated by reference.